Bacillus stercoris and Enterobacter quasihormaechei as phosphate-solubilizing bacteria: Isolation, characterization, and abiotic stress response

Phosphobacteria are key suppliers of phosphate, a crucial nutritional component for plant growth. After being isolated from the rhizosphere of vegetable plants, a total of 20 phosphate-solubilizing bacteria (PSB) were tested for their ability to dissolve phosphate in soil and promote plant growth by producing phytohormones. Only two of the twenty isolates tested positive by converting to dark pink, and these bacteria were capable of producing phytohormones (auxin). Hence, these bacteria were selected for further investigation after testing positive for auxin production. Auxin is regarded as a vital regulator, particularly for plant growth. It regulates seed germination and elongation of the plant’s roots and shoots. After screening for phosphate-solubilization activity, it was revealed that the phosphate-solubilizing index of these isolates was recorded as 3.16 and 3.33. Under in vitro conditions, both plant growth-promoting bacteria were further studied for growth up to 72 h in terms of salinity, pH, and temperature. In this study, both P7 and P9 isolates showed maximum growth at pH 7.0 and 9.0, temperatures of 30°C and 47°C, and salinity of 4% and 10%, respectively. In addition, biochemical tests and 16S rRNA gene sequence analysis were done, identifying isolates P7 and P9 as Bacillus stercoris and Enterobacter quasihormaechei, respectively. This study emphasizes that B. stercoris and E. quasihormaechei can be advantageous in sustainable agriculture by optimizing plant growth and increasing crop output.